In the art of machine tools, it is common to utilize a workpiece support table or surface which is interrupted by parallel spaced slots each having an inverted T-shaped configuration. The workpiece is clamped to the surface by one or more bar-like clamping devices such as, for example, disclosed in U.S. Pat. No. 3,451,668. The bar clamps are secured to the supporting surface by threaded fasteners which connect with T-nuts positioned within the slots as shown in the above patent. Frequently, it is desirable to clamp a workpiece to a supporting surface by engaging only edge surfaces of the workpiece with adjustable jaw clamps having a low profile so that the clamps do not project substantially from the supporting surface and do not interfere with the operation to be performed on the workpiece.
One form of adjustable jaw workpiece clamp is disclosed in U.S. Pat. No. 3,506,253 and incorporates a screw projecting through an inclined hole within an adjustable jaw. The screw is threaded into an aligned hole within a nut member adapted to be received within a T-slot. Another form of adjustable jaw clamp incorporates a clamping plate or bar having a sloping or inclined forward surface with a dovetail guide which receives a jaw element. The jaw element is adjusted along the inclined dovetail guide by rotating an adjustment screw captured between the jaw and the dovetail guide. Such a clamping device is manufactured and sold by J & S Tool Co., Inc., Livingston, N.J. Another form of a device for gripping and holding an edge surface of a workpiece is disclosed in U.S. Pat. No. 1,938,337 wherein a workpiece gripping element is slidably supported within a slightly inclined slot formed within a clamp body, and a horizontal adjustment screw is rotated for moving the gripping element within the slot.